FRF measurements on slowly time-varying systems using multisines with non-uniformly spaced harmonics

Recently [1] a method has been developed to detect and quantify the influence of time-variation in frequency response function measurements using random excitations. This method can also be applied to random phase multisine excitations, provided uniformly spaced excited harmonics. However, in quite some applications a non-uniform harmonic spacing is required, for example, a quasi logarithmic spacing to cover a large frequency range, and a random spacing to detect and quantify nonlinear distortions. In this paper we extend the results of [1] to random phase muItisines with non-uniformly spaced harmonics.